1. Field of the Invention
The present invention generally relates to a method of driving a display, a display, a drive signal processor, a computer program for the same, and a computer-readable storage medium with the program recorded thereon.
2. Description of Related Art
Liquid crystal displays with low operating power are in widespread use not only in mobile devices but also in stationary types. In comparison to the CRT (Cathode-Ray Tube) and the like, the liquid crystal display is slow to respond and may fail to completely respond within a rewrite time (16.7 msec) which corresponds to a typical frame frequency (60 Hz) depending on grayscale level. This issue is addressed in, for example, Japanese published unexamined patent application 2002-116743 (Tokukai 2002-116743; published Apr. 19, 2002) by driving the LCD (liquid crystal display) with a drive signal that is modulated for a quick transition from a current to a desired grayscale level.
For example, supposing that a grayscale level transition from a current frame FR(k−1) to a next frame FR(k) requires a “rise” drive. If so, a voltage is applied to a pixel so as to facilitate a transition from the current grayscale level to a desired grayscale level. Specifically, a voltage applied to the pixel is higher than that represented by video data D(i,j,k) for the next frame FR(k).
In grayscale level transition, the application of the voltage increases the brightness level of the pixel more quickly and takes less time to raise it to a proximity of the brightness level indicated in the video data D(i,j,k) for the next frame FR(k) than the faithful application of an exact voltage represented by the video data D(i,j,k) for the next frame FR(k).
However, the liquid crystal response speed may be grossly insufficient, and a suitable transition from the current to a desired grayscale level could become impossible even with a facilitation. An insufficient response may occur if the processing circuitry which determines and executes the facilitation assumes that the transition was sufficiently performed from the previous grayscale level to the current grayscale level, despite a fact that a targeted brightness level was not actually reached in the transition from the previous grayscale level to the current grayscale level.
Meanwhile, Japanese patent 2650479 (issued Sep. 3, 1997) describes a display which predicts a transmittance curve from a pixel's signal data for at least three successive fields. If the predicted transmittance curve is off a desired transmittance curve by a predetermined value or more, the display corrects the signal data for the successive fields.
FIG. 11 is a block diagram of part of a prior art display. Referring to FIG. 11, in a display 101, video data from a data input means 111 is stored by a field memory 112 before the video data is transferred to a pixel. A data correcting means 113 refers to the field memory 112 and, if a predetermined threshold value is exceeded by a difference between the predicted transmittance and an ideal transmittance, the data correcting means 113 corrects the video data in the field memory 112. A data output means 114 then sequentially reads out the corrected video data in the field memory 112 to drive the pixel (not shown in the figure).
The prior art structure of FIG. 11 thus stores corrected video data in the field memory 112. Reference is then made to the video data when the pixel is driven in the next field, to determine the need for a correction and to perform the correction. Any deviations of a predicted transmittance from an actual transmittance would be cause for an accumulative correction error. To avoid such correction errors, the prediction should be sufficiently accurate. However, enabling sufficiently accurate prediction may be difficult to accomplish absent complex, relatively large and hence costly circuitry.